(a) Field of the Invention
The present invention relates to a plasma display panel (referred to hereinafter simply as a “PDP”) which involves enhanced discharge stability and luminescence efficiency in displaying images.
(b) Description of Related Technology
Generally, a PDP is a display device which displays images using red, green, and blue (R, G, and B) visible rays. The visible rays are generated by exciting phosphors with the use of vacuum ultraviolet rays, which are radiated from plasma obtained through gas discharge. The PDP can provide a large-sized screen of sixty inches or greater with a thickness of only 10 cm or less. The PDP is a self light-emitting display device such as a CRT, and does not suffer distortion due to color representation or viewing angle. Furthermore, compared to an LCD, the PDP involves simplified processing steps, economical production costs, and excellent productivity, and hence has been spotlighted as a flat panel display for TV and industrial purposes.
In an AC PDP (Alternating Current PDP), address electrodes are formed on a rear substrate in one direction, and a dielectric layer is formed on the entire surface of the rear substrate covering the address electrodes. Stripe-patterned barrier ribs are formed on the dielectric layer such that they are disposed between neighboring address electrodes, and red, green, and blue (R, G, and B) phosphor layers are formed between neighboring barrier ribs.
A pair of display electrodes, having transparent electrodes and bus electrodes, are formed on the surface of a front substrate facing the rear substrate. A dielectric layer and an MgO protective layer are generally sequentially formed on the entire surface of the front substrate while covering the display electrodes.
The discharge cells are formed at the crossed regions of the address electrodes of the rear substrate and the pair of display electrodes of the front substrate.
Millions of unit discharge cells are arranged within the PDP in the shape of a matrix. Memory-based driving is conducted to simultaneously drive the AC PDP discharge cells arranged in the matrix shape.
Specifically, a potential difference of at least a predetermined voltage should be generated between the X electrode (sustain electrode) and the Y electrode (scanning electrode) of the display electrodes to generate the discharge. The predetermined voltage is called a firing voltage Vf. When the scan voltage is applied to the Y electrode and the address voltage to the address electrode, a discharge is fired while forming plasma within a designated discharge cell. Also, the electrons and ions existent in the plasma are transferred to the electrode with opposite polarity, thereby creating an electrical current flow.
In addition, a dielectric layer is deposited on the respective electrodes of the AC PDP, and most of the transferred space charges are deposited on the dielectric layer with opposite polarity. Accordingly, the net space potential generated between the Y electrode and the address electrode becomes smaller than the initially applied address voltage Va, thereby weakening the discharge and dissipating the address discharge. At this time, a relatively small amount of electrons are deposited on the X electrode, and a relatively large amount of electrons are deposited on the Y electrode. The charges deposited on the dielectric layer covering the X and the Y electrodes are called wall charges Qw. The space voltage formed between the X and the Y electrodes due to the wall charges Qw are called a wall voltage Vw.
Under the application of a predetermined voltage (the sustain voltage Vs) between the X and the Y electrodes, when the sum Vs+Vw of the sustain voltage Vs and the wall voltage Vw is higher than the firing voltage Vf, the discharge is generated within the discharge cell while generating vacuum ultraviolet (VUV) rays. The vacuum ultraviolet rays excite the corresponding phosphors so that visible rays are emitted through the transparent front substrate.
In contrast, when the address discharge is not made between the Y electrode and the address electrode (that is, with no application of the address voltage Va), the wall charges are not deposited between the X and Y electrodes, and accordingly, the wall voltage is not present between the X and Y electrodes. In this case, only the sustain voltage Vs applied between the X and Y electrodes is formed within the discharge cell. As the sustain voltage Vs is lower than the firing voltage Vf, the gas discharge between the X and Y electrodes does not occur.
The PDP is generally influenced by discharge stability and display brightness depending upon the shape of the phosphors formed at the barrier ribs of the discharge cells. Furthermore, the vacuum ultraviolet rays generated due to the gas discharge do not excite the entire phosphor layers, formed within a given discharge cells, and being very thick, but only excite one or two of the outermost layers of phosphors so that the luminescence efficiency of the PDP is reduced.